$ { {-5} \times \left[\begin{array}{rrr}{3} & {-2} & {-1} \\ {-2} & {3} & {-1}\end{array}\right] = {?} } $
To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{-5}\times{3} & {-5}\times{-2} & {-5}\times{-1} \\ {-5}\times{-2} & {-5}\times{3} & {-5}\times{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-15} & {10} & {5} \\ {10} & {-15} & {5}\end{array}\right]}$